Endoscopic procedures in the kidney rely on two primary approaches: retrograde and antegrade instrumentation of the upper urinary tract. The retrograde approach utilizes ureterorenoscopy to traverse the urethra and ureter, while antegrade instrumentation requires a percutaneous puncture directly into the kidney. Both approaches must respect the intrarenal anatomy just as in open renal surgery, and imaging is required for safety.
PERCUTANEOUS RENAL ACCESS
To safely enable percutaneous renal access, the most important principle is to identify a puncture direction that will provide direct access to the target and safe, bloodless instrumentation. Visualization of both the puncture needle and the target and precise guidance of the needle tip to the target require imaging techniques such as ultrasound, fluoroscopy, and, in selected cases, computed tomography (CT).
Contraindications to percutaneous kidney puncture are blood-clotting anomalies due to coagulopathies or pharmacologic anticoagulation. Sterile preparation and draping of the surgical field are required in the same way as for open surgery, although these procedures are generally categorized as clean-contaminated and not sterile given entry into the genitourinary tract. Local anesthesia suffices only for puncture of the kidney and small-bore tract dilation (6–12Fr), for antegrade insertion of a ureteral stent or nephrostomy catheter. Lidocaine hydrochloride 2% USP, 10 mL, can be given for infiltration of the skin and tissues along the intended tract of puncture down to the renal capsule. For larger-bore tract dilation of ≤30Fr, general anesthetic is usually recommended for both patient comfort procedural accuracy, although local or regional anesthetic can be used when absolutely required.
IMAGING AND PUNCTURE TECHNIQUES
Percutaneous puncture of the renal collecting system may be performed for diagnostic procedures (eg, antegrade pyelography, pressure/perfusion studies) or to establish access for therapeutic interventions (Table 9–1).
Table 9–1.Indications for percutaneous puncture of the renal collecting system. |Favorite Table|Download (.pdf) Table 9–1. Indications for percutaneous puncture of the renal collecting system.
Pressure/perfusion study (Whitaker test)
Nephrostomy catheter drainage
Antegrade ureteral stenting
Dilation of ureteral strictures
Percutaneous resection and coagulation of urothelial tumors
Both ultrasonic scanning and fluoroscopy provide visualization and guidance for a safe, accurate percutaneous puncture, but ultrasound has the following definite advantages:
Shorter learning curve to master renal access compared to fluoroscopic guidance
Easier identification of posterior calyces for safe renal entry
No intravenous or retrograde administration of contrast dye
No radiation exposure
Continuous real-time control of puncture
Imaging of radiolucent, non-contrast-enhancing renal and extrarenal structures (eg, renal cyst, retroperitoneal tumor) for puncture
Imaging of perirenal structures that should be avoided during needle passage (eg, bowel, lung, liver, spleen)
Reduced cost relative to fluoroscopic guidance
Fluoroscopy may be easier to use in the nondilated collecting system or in the presence of staghorn ...